Modulator with improved damping

Abstract

A modulator with improved damping comprises a charging network which limits the rate at which energy is transferred into a pulse forming network, and a switch to discharge the energy stored in the pulse forming network when the network has charged to a predetermined energy level. The pulse forming network discharges into the primary winding of a transformer which couples the energy to its secondary winding which routes the energy to an RF power generating tube. The modulator also includes an improved damping network which places a diode and resistor electrically in parallel with each other, and both in series with the switch to reduce the magnitude of the post-pulse voltage oscillations.

I claim: 
     
       1. An improved line-type modulator which receives electrical power from a source, and provides a pulse of electrical energy to an R.F. power tube, comprising: a charging circuit comprising an inductor having a first lead through which said electrical current from the source is received and a second lead tied to an anode of a hold-off diode through which current flows at a limited rate;   a pulse forming network having a high side and low side, receives electrical current and charges to a predetermined level of energy with electrical current from said charging circuit received through said high side;   a pulse transformer having a primary winding coupled to said pulse forming network low side and a secondary winding coupled to the R.F. tube;   switching means for triggering the discharge of energy stored in said pulse forming network to said transformer when the energy in said pulse forming network reaches the predetermined level;   an inverse damping circuit having a second resistor and second diode in series, with the cathode of said second diode connected to said high side of said pulse forming network, and a lead of said resistor connected to a return line;   a backswing damping circuit having a third diode and a third resistor connected in series, with the anode of said third diode connected to said low side of said pulse forming network, and a lead of said third resistor connected to said return line; and   wherein the improvement comprises,   a damping network comprising a first diode and a first resistor connected electrically in parallel, and each connected in series with said switching means, such that said damping network reduces the magnitude of the post pulse voltage oscillations in the modulator.   
     
     
       2. The improved line type modulator of claim 1, wherein the anode of said first diode and a first lead of said first resistor are both connected to the cathode of said hold-off diode, and the cathode of said first diode and the second lead of said first resistor are both connected to a first lead of said switching means, and a second lead of said switching means is connected to said return line. 
     
     
       3. The improved line type modulator of claim 1, wherein a first side of said switching means is connected to the cathode of said hold-off diode, and a second side of said switching means is connected to both the anode of said first diode and the first lead of said first resistor, and the cathode of said first diode and the second lead of said first resistor are both connected to said return line. 
     
     
       4. The improved line type modulator of claim 2, wherein said switching means comprises a gas tube switch. 
     
     
       5. The improved line type modulator of claim 2, wherein said switching means comprises a solid state switch. 
     
     
       6. The improved line type modulator of claim 2, wherein said switching means comprises a magnetic core switch. 
     
     
       7. A line type modulator which receives power from an electrical current source and provides a pulse of electrical energy to an RF power tube, comprising: an electrical pulse forming network having a high side and a low side;   a charging circuit comprising an inductor having a first lead through which said inductor receives electrical current from the source, and having a second lead tied to an anode of a hold-off diode through which current flows at a limited rate to charge said pulse forming network connected to the cathode of said hold-off diode, where the impedance of said inductor limits the rate at which energy can be delivered from the source to said pulse forming network high side;   a pulse transformer which receives electrical energy from said pulse forming network low side and couples the pulse of electrical energy to the RF tube;   switching means for triggering the discharge of the energy within said PFN to said pulse transformer; and   a damping circuit comprising a first diode and first resistor connected electrically in parallel with each other, and both in series with said switching means, for dissipating the residual energy associated with the stray capacitance of said switching means and the RF tube to reduce the post pulse voltage oscillations in the modulator;   an inverse damping circuit having a second resistor and second diode in series, with the cathode of said second diode connected to said high side of said pulse forming network, and a lead of said resistor connected to a return line; and   a backswing damping circuit having a third diode and a third resistor connected in series, with the anode of said third diode connected to said low side of said pulse forming network, and a lead of said third resistor connected to said return line.   
     
     
       8. The improved line type modulator of claim 7, wherein the anode of said first diode and a first lead of said first resistor are both connected to the cathode of said hold-off diode, and the cathode of said first diode and the second lead of said first resistor are both connected to a first side of said switching means. 
     
     
       9. The improved line type modulator of claim 7, wherein a first side of said switching means is connected to the cathode of said hold-off diode, and a second side of said switching means is connected to the anode of said first diode and a first lead of said first resistor, and the cathode of said first diode and the second lead of said first resistor are both connected to said return line. 
     
     
       10. The improved line type modulator of claim 8, wherein said switching means comprises a gas tube switch. 
     
     
       11. The improved line type modulator of claim 8, wherein said switching means comprises a solid state switch. 
     
     
       12. The improved line type modulator of claim 8, wherein said switching means comprises a magnetic core switch.